W3C published the initial RDF Model
and Syntax Specification in 1999. Use of RDF data has lead to the
development of several
RDF Query languages. It is hoped that a recommended query language will
reduce redundancy and enhance interoperability as SQL did for relational
databases. This document defines a two-part charter for the RDF Data Access
Working Group. In the first phase, the WG will evaluate requirements and
select a strawman RDF query language, or document why divergent requirements
make this impossible. If a strawman is selected, the WG will enter the second
phase in which it will write a formal specification and test cases for this
language.

The RDF data model is a directed, labeled graph with edges
labeled with URIs and nodes that are either unidentified, literals, or URIs
(please see the RDF Primer for further explanation).
The principal task of the RDF Data Access Working Group is to gather
requirements and to define an HTTP and/or SOAP-based protocol for selecting
instances of subgraphs from an RDF graph. The group's attention is drawn to
the RDF Net API submission. This will involve a language for the
query and the use of RDF in some serialization for the returned results. The
query langauge may have aspects of a path language similar to XPath (used for
XML in XSLT and XQuery) and various RDF experimental path syntaxes.

The requirements document will assist in the selection of a strawman query
language. The working group will evaluate expressivity needs and other
constraints gathered during the requirements phase and select a starting point for
design from a list of existing query langauges (eg RDQL, XQuery, RuleML,
N3). This query language is
to be used as a starting point for phase 2. If the working group is unable to
select a query language that meets, or can meet, the requirements, it will
document the reasons this is not possible and either adjourn or ask the
Advisory Committee to re-charter the working group.

This completes phase 1 of the working group charter. If a strawman is
selected, the working group will continue with phase 2 without further review
by the Advisory Committee.

Specification of an abstract syntax promotes interoperability between
alternate serializations and APIs. It also helps illustrate the commonalities
and differences with other query languages. The working group will produce an
abstract syntax for the query language and protocol.

At this stage, it is not clear to what extent XQuery technology is
applicable to the task of querying RDF datasets.
The RDF DAWG should aim to maximize W3C technology
re-use, while also taking account of differences
between the RDF graph data model and the XQuery data model.

There is a requirement for RDF data to be accessable within an XML Query context.
The working group should specify at least one mechanism for exposing
RDF query facilities in an XQuery environment; that is, a way to take a piece of RDF Query abstract syntax and map it into a piece of XML Query using some form of extension to XQuery.
The working group should examine TreeHugger and XQuery with
Functional Accessors in their discussion of the use of XQuery with RDF.

While the data model of the query language of this protocol is dissimilar to
that of XQuery, a non-XML concrete syntax might reuse syntactic elements from
XQuery to aid learning time, even if XQuery is not chosen as the strawman.

The working group will need to make trade-offs in accepting query
requirements that are practical for use in general semantic web applications while maintaining a simple,
easy to implement query mechanism. Many of these trade-offs will affect
expressivity, eg disjunction, negation (of various forms), optional relations
or node identification. The Requirements Document and test cases will provide the working group with guidance in making these trade-ffs.

The working group must recognize that RDF graphs are often constructed by
aggregation from multiple sources and through logical inference, and that
sometimes the graphs are never materialized. Such graphs may be arbitrarily
large or infinite.

The protocol will allow access to a notional RDF graph. This may in
practice be the virtual graph which would follow from some form of inference
from a stored graph. This does not affect the data access protocol, but may
affect the description of the data access service. For example, if OWL DL
semantics are supported by a service, that may be evident in the description
of the service or the virtual graph which is queried, but it will not
affect the protocol designed under this charter.

While it is hoped that the product of the RDF Data Access Working Group
will be useful in later development of a rules language, development of such a rules language is out of scope for
this working group. However, any serializations of a query
language must not preclude extension to, or inclusion in, a rules language.
The group should expend minimal effort assuring that such an extension be
intuitive and and consistent with any query language produced by the
group.

Some languages, for instance, OQL, define a layer of protocol that
handles requester/server interactions for result set cursors or proofs. The
abstract syntax may be extensible to express the relevant parameters, but
their definition and effects are beyond the scope of this working group.

Some existing protocols, such as the RDF
Net API, define operations for changing a graph. The RDF Data
Access Working Group is only required to defined a protocol for
conveying queries and their results. However, the group should be
aware that it is likely that their work will be extended to support
modifying the graph and should expend reasonable effort to ensure that
such extension is easy, moreover, the group may include such an
ability.

The RDF Data Access Working Group will discuss use cases and
evaluate the requirements. The group should pick an existing query
language or draft a straw-man. This language will allow the
Working Group to begin developing test materials. Throughout
development, the working group will maintain test cases to reflect
issue resolution and aid in conformance evaluation.

W3C has 3 recommendations in the area of selecting from XML infosets: XPath, XQuery and XSLT.
While RDF query addresses a different data domain (the RDF graph), any query
mechanisms defined by this group must leverage off, and, where possible,
interoperate with, the related XML recommendations.

The XPath language defines a non-XML syntax for addressing subtrees
from XML documents. It factors out the selection functionality common
to XQuery and XSLT. It is hoped that RDF Query will provide analogous
functionality for addressing subgraphs. The working group will adopt, or
define relationships with, applicable portions of the XPath data
model.

Proper layering of RDF languages is crucial to the integrity of the Semantic Web. Each deliverable of any Working Group must
satisfy the dependencies from other W3C Working Groups before it can advance
to Candidate Recommendation.

While each charted RDF working group is responsible for the soundness
of the interactions between their product and other RDF-related work,
the RDF Core Working Group is in a unique position to provide oversee
this process. The RDF Core is responsible for the RDF data model. The
RDF Data Access Working Group must provide a query mechanism for
selecting data from this model or document to the RDF Core Working
Group's satisfaction the impracticality/impossibility of doing so.

OWL provides a set of terms and semantics that must be
queryable by the product of the RDF Data Access Working Group. As stated above, the ability of a data store to
perform inferences is outside the scope of this group.

The RDF Core and WebOnt working groups' charters are expected to
expire before the DAWG publishes its first working draft. The Semantic
Web Best Practices and Deployment (SWBPD) Working Group will be meeting
when these groups terminate so the DAWG will seek its architectural review.

The RDF Data Access WG and the Internationalization
Working Group will work together to clarify and resolve
internationalization and localization issues in XML Schema, and
will jointly ensure that it satisfies W3C goals for international
access to the Web.

The group's attention is drawn to the fact that many Internet protocols
involve data access, for example LDAP, IMAP, WebDAV. It is not intended that the data access protocol
perform tasks for which these protocols were designed. However,
they may provide a source of instructive use cases.

To become a member of the RDF Data Access Working Group, a representative
of a W3C Member organization must be nominated by their Advisory Committee
Representative. The appropriate process will be identified in the Call for
Participation.

Each W3C Member organization is limited to at most one
principal participant and one alternate participant of
this Working Group. Attendance by an alternate discharges the principal's
attendance obligations.

Participation is also open to invited experts from the
community, selected by the chair, in accordance with the Invited
Experts provisions in the Process Document, in order to balance the
technical experience of the group. Invited experts participate as
principals.

Participation is expected to consume at least one day per week of each
Working Group participant's time.

The Working Group's technical discussions will occur on the public mailing
list public-rdf-dawg.
All technical documents and decisions will be made available to the public
through the Working Group's process.

The Working Group will use a home
page to record the history of the group, and which will provide access to the archives,
meeting minutes, updated schedule of deliverables, membership list, and
relevant documents and resources. The page will be available to the public
and will be maintained by the Chair in collaboration with the W3C team
contact. This page will be linked from the RDF home
page.

A one to two hour Working Group phone conference will be held every week.
When necessary to meet agreed-upon deadlines, phone conferences may be held
twice a week. Each principal (or alternate) participant is expected to participate in phone conferences. The
Chair may, at his or her discretion, invite guest experts to attend particular phone
conferences.

Meeting records should be made available within three days of each
telephone meeting. Meeting records must be made publicly available except for
non-technical issues that do not directly affect the output of the Working
Group. The Chair decides which issues are not made public.

Participation in face-to-face meetings is limited to working group members
and observers invited by the Chair. Decisions may be taken in
face-to-face meetings but must be announced on the Working Group mailing
list. Observers may take part in decision-making at the discretion of the
Chair.

In addition to the required face-to-face meetings, the
Working Group may schedule other face-to-face meetings in a manner that
maximizes co-location with events that Working Group members would be
attending anyway.

The Chair makes Working Group meeting dates and locations available to the
group at least eight weeks before the meeting, per W3C
Process.

To be successful, we expect the Working Group to have approximately 10 to
15 participating Member organizations and invited experts for its duration. We also expect a large
public review group that will participate in the mailing list discussions.

This Working Group operates under the W3C Patent Policy (5 Feb 2004
Version). To promote the widest adoption of Web standards, W3C seeks to
issue Recommendations that can be implemented, according to this policy, on a
Royalty-Free basis. The inclusion of the new Patent Policy in the charter is
contingent upon successful completion of AC review of the Process Document
and Patent Policy Transition Procedure.